1. Field of the Invention
The present invention relates to the unit and method for transmitting setup-change instructions according to the order of the products which flow through respective production units as well as estimates of the loads on the respective production units in a production line. Further, the present invention also relates to a production system which is equipped with a setup-change instruction unit.
2. Description of the Related Art
In a production line which is not specialized in a particular product allowing a variety of products to flow thereon, determining when the setup of each processing unit should be changed is a very important factor which affects the amount and the timing of production of the production line. However, the loads on respective production units in the production line may change because the production order and required time vary depending on the product type. Thus, conventionally, a production unit which has the heaviest load is selected according to the work-in-progress condition of the production line, the order of production in that production unit is determined and then the same order is given to the other units as an instruction for setup-change.
However, as described above, the loads on respective production units change depending on the product type and a bottlenecked production unit which has the heaviest load also changes. Further, some production units are sometimes stopped due to problems or inspection. The load on respective production units always changes with the passage of time. Therefore, in the prior art, a change of the load has been coped with by the operator checking the load repeatedly in short intervals. For this reason, it takes time and effort to determine the timing of setup-change and it is difficult to determine the timing of setup-changes accurately.